This invention pertains to vehicular windshield wiper installation.
Most of today's standard wiper installations are driven by a motor via a gear inserted behind said motor in the following manner: The armature shaft of an electric motor carries a worm mating with a worm wheel being accomodated in a gear housing. The worm wheel may be considered as the drive unit for a driven motor shaft which as a separate part is fixed on the worm wheel torsionally firm and guided in a bearing bore of the gear casing. On the driven-end side of this shaft a crank is secured as a driven unit. The crank co-operates with at least one push rod which is articulated on a pivot pin of a further crank. This second crank can again be designated as drive unit for a wiper shaft which is guided in a wiper bearing fixed on the body of the vehicle and which on its driven-end side carries a fastening member of a wiper arm. In this manner the rotary movement of the armature of the electric motor and thus the rotary movement of the driven motor shaft is transformed into a pendulum movement of the wiper shaft and thus of the wiper.
Up to now, the various parts of this gear have been mostly produced in separate courses of manufacture and been secured on each other later, thus requiring further phases of operation. Normally the driven motor shaft is made of steel and is pressed into the worm wheel made of laminated fabric material. Also the actual wiper shaft as well as the crank fastened on it and the pivot pin are ususally made of steel, whereby these parts have mostly been riveted, caulked or welded with each other. The production of such wiper installations is therefore relatively complicated and expensive. Due to the steel parts predominantly used the weight is relatively high.
The invention is therefore based on simplifying production of the various gear parts of such a wiper installation in a way that, in comparison to known wiper installations, advantages with regard to costs and weight are achieved.
German patent application No. 1,196,523 published for opposition describes a wiper installation in which a shaft bored through eccentrically is formed on a worm wheel and the shaft is guided in a bearing of a gear casing. However, in contrast to the hints in the description of this prior publication, the shaft does not transmit the torque from the worm wheel to the motor crank. The crank is fixed on a crank shaft mounted in the eccentric bore. The crank shaft may be coupled torsionally firm with the worm wheel via a locking mechanism. Thus, the shaft end only serves to support the worm wheel and to displace the crank center of rotation when the torsionally firm coupling between worm wheel and crank shaft is discontinued for the purpose of entering the wipers into a so-called submerged parking position.
In German Pat. No. 2,010,922, the wiper shaft and the crank are developed in one piece as a metal support forming an angle, whereby the wiper shaft portion is coated with plastic material by injection molding. The end portion of the metal support facing the crank is bent in a hook-shaped manner and a plastic ball member for articulating a push rod is injection-molded thereon. Thus, the torque is carried by the drive unit, namely the crank, to the driven unit, namely the wiper arm and its link respectively, via a metal wiper shaft.
In the known versions, both the motor shaft and the wiper shaft have a conical, externally toothed portion and a following portion with an external thread. Because the diameter of the shaft is made as small as possible, due to the costs involved and in order to save weight, the number of teeth on the outer circumference of the conical portion is relatively small as well. Therefore, the motor crank and the fastening member of the wiper arm respectively can often not be secured in exactly the right position with respect to the shaft. Besides the necessary torque often can not be transmitted via this small number of teeth. This is the reason why it is necessary to brace the driven unit with the shaft by means of a nut screwed onto the external thread portion.